Rotary chucking cylinder for machine tool

ABSTRACT

A cylinder piston unit which is controlled by a pressure fluid for operating a chucking tool comprising a valve unit having two check valves and a small intermediate control piston within a transverse bore in a hub of the piston shaft, which hub has a diameter equal to the total length of the valve unit. The valve unit is held in place by a single locking ring.

Unite tates Patent 72] Inventor Gunter Horst Rohm Sontheim, Germany [21] Appl. No. 20,671

[22] Filed Mar. 18, 1970 [45] Patented Aug. 17,1971

[73] Assignee Rohm-Gesellschaft m.b.11., Werkzeug-und Maschinenfabrik Sontheim-Brenz, Germany [32] Priority Apr. 11, 1969 [3 3 Germany [54] ROTARY CHUCKING CYLINDER FOR MACHINE TOOL 2 Claims, 1 Drawing Fig.

[52] 11.8. CI 91/420, 91/422, 279/4 [51] llnt.Cl ..lF15b 11/08, F15b 13/042 [50] lField '01 Search 91/420, 422; 92/106; 279/4 [56] References Cited UNITED STATES PATENTS 2,964,016 12/1960 Talak 91/420 3,126,706 3/1964 Dettingerm 91/420X 3,369,464 2/1968 Blattry 91/420 3,411,415 11/1968 Benjamin et a1. 91/420 Primary Examiner-Martin P. Schwadron Assistant Examinerlrwin C. Cohen Att0meyOtto John Munz ABSTRACT: A cylinder piston unit which is controlled by a pressure fluid for operating a chucking tool comprising a valve unit having two check valves and a small intermediate control piston within a transverse bore in a hub of the piston shaft, which hub has a diameter equal to the total length of the valve unit, The valve unit is held in place by a single locking ring.

P-ATENTED AUEIYIBII GUNTER HORS HM ROTARY CHUCKTNG CYLINDER FOR MACHINE TOQL The present invention relates to improvements in a rotary chucking cylinder of the type as described and claimed in the copending application of Rudi Kodalle, Ser. No. 5,305 filed on Jan. 23, 1970, and also assigned to the assignee of the present application. This chucking cylinder is designed for tightening and releasing a chucking tool of a lathe or other machine tool by means of a pneumatic or hydraulic pressure medium which acts upon a piston which is axially slidable within the cylinder and mounted on a shaft which is connected to and rotatable within a distributor housing This shaft is provided with two channels each of which has one end communicating with a connection fitting on the distributor housing for the supply and discharge of the pressure medium, while its other end leads to the cylinder chamber at one or the other side of the piston. The flow of the pressure medium through the two channels is controlled by a pair of check valves in such a manner that the pressure of this flow through one channel opens both check valves and the medium then flows through one of these valves into one cylinder chamber and thereby shifts the piston, while the pressure medium which is thereby expelled from the other cylinder chamber flows off through the other check valve and the other channel.

It is one of the objects of this prior invention to design the chucking cylinder so that the movements of its piston are transmitted to the outside where they may be employed for indicating the operating positions of the piston and/or for supervising or controlling the operations of the machine tool. For attaining this object, the .check valves of this chucking cylinder are mounted on the piston within the cylinder so as to be bodily movable with the piston but to operate in a direction transverse to the axial movements of the piston, and the shaft of the piston which contains the channels for supplying and discharging the pressure medium is mounted in the front and rear walls of the cylinder so as to be rotatable with the cylinder but slidable in its axial direction and to project from the rear wall of the cylinder to the outside. On this projecting part of the shaft the distributor housing is mounted so as to be nonrotatable but to be taken along by this shaft when it is moved in its axial direction. The axial movements of the shaft of the piston are thus directly transmitted to the distributor housing which carries or is operatively associated with suitable means for indicating the different operating positions of the piston and/or for employing the movements of the piston for supervising or controlling the operations of the machine tool. Each of the two check valves of the chucking cylinder according to this prior invention which are mounted on the piston corn prises a valve cage containing a valve chamber which has an aperture in its bottom forming a valve seat which communicates with one of the channels and is normally closed by a valve plate and may be opened toward the inside of the valve chamber against the action of a spring by the force of the pres sure medium which is supplied through the mentioned channel and which then flows from the valve chamber through a valve port toward one or the other cylinder chamber. The two check valves may be combined so as to form a single structural unit which is mounted in a bore in the piston which extends transverse to the piston axis so that the two valve chambers are disposed in this housing diametrically opposite to each other at both sides of the piston axis and are separated from each other by an intermediate central cylindrical chamber in which a small control piston is slidable which has a tappet pin projecting from each of its opposite ends which is adapted to act upon the valve plate of one of the valves so as to open the same against the action ofits spring.

In order to hold the mentioned valve unit or its three main components, i.e. the two check valves and the intermediate control piston in a fixed position within the transverse bore in the piston, it is necessary to provide the wall of this bore with annular grooves into which spring rings are snapped which engage upon the outer ends of the check valves, In the production of a chucking cylinder as described above it has been found very difficult to cut these annular grooves into the wall of the bore into which the spring rings are to engage, and it is also difficult to insert this valve unit or its components into the much longer bore in the piston so as to be in the proper central position therein.

it is therefore an object of the present invention to provide a chucking cylinder which is of the same general design as previously described but may be more easily manufactured and also permits the valve unit or its main components, i.e. the two check valves and the small intermediate control piston, to be more easily installed in or on the piston and to be locked thereto without requiring annular grooves to be cut into the piston for holding spring rings.

According to the present invention this object is attained in the following manner: Instead of providing the piston with a transverse bore which extends through its entire diameter and in the wall of which the annular grooves have to be cut to hold the spring rings and thus the valve unit or its components in a fixed position, the present invention provides that the thickness of the piston as seen in its axial direction is considerably reduced and that in place of the reduced part the piston or piston shaft is provided with a hub which is located between the front surface of the piston and the end of the shaft which projects through the cylinder cover and has a diameter which is much smaller than that of the piston and is equal to the total length of the entire valve unit or its components. This hub is now provided with a diametrical bore which intersects and communicates with the ends of the two channels in the shaft and is adapted to receive the valve unit or its mentioned components. For securing the valve unit in a fixed position in this bore, a ring is slipped in the axial direction over the outer peripheral surface of the hubs so as to cover the outer ends of the bore and engage with the opposite ends of the valve housing. This ring is preferably provided in the form of a spring ring.

Aside from the fact that by the provision of this hub the weight and volume of the piston is considerably reduced, the invention produces the particular advantage that only a single ring is needed for locking the entire valve unit to the piston in the exact position as required, and that this ring may be very easily slipped over the free end of the hub before the shaft car rying the piston is inserted into the open cylinder which is thereafter closed by the cover. Thus, for locking the valve unit in a fixed position to the piston or its shaft, no difficult and expensive groove-cutting operations have to be carried out in the transverse bore for holding small spring rings, and the valve unit may also be much more easily installed in the short transverse bore of the hub.

The features and advantages of the present invention will become further apparent from the following detailed description which is to be read with reference to the accompanying drawing which shows a longitudinal section of the chucking cylinder according to the invention.

The chucking cylinder as illustrred in the drawing comprises a cylinder 1, a piston 2 which is axially sli ble within cylinder 1 but rotatable together with the cylinder, and a shaft 7 which is secured to or integral with piston 2 and projects from both sides of the piston and extends slidably through if rear wall and the cover of the cylinder to the outside. The for wardly projecting end of shaft 7 is provided with a tapped bore 3 into which the threaded end of a rot (not shown) of the chucking tool may be screwed which usually extends through the hollow spindle of the machine tool to the rear end of which the cover of cylinder 1 is to be secured so that the cylinder together with piston 2 and shaft 7 will be rotated by the spindle.

By means of shaft 7, cylinder 1 is connected to a distributor which is generally designated by the numeral 4 and comprises a distributor housing 5 which is mounted so as not to be rotatable with shaft 7 but is connected to the latter so as to follow its movements in axial directions. For this purpose, shaft 7 is rotatably mounted within the distributor housing 5 on bearings near the opposite ends of the housing in a manner so as to be substantially immovable in its axial direction relative to shaft 7. The rear wall of cylinder 1 is further provided with suitable gaskets 16 which surround the shaft 7 and seal the cylinder relative to the outside while permitting the shaft to slide in its axial direction relative to the cylinder. Thus, any axial movements of piston 2 in the direction of the double arrow 17 will be positively transmitted by shaft 7 to the distributor housing 5 from which they may be further transmitted to suitable indicating means or a control device, for example, an electric switch, by suitable cam means 37 or the like which may be removably mounted on the connection fittings 6 on the distributor housing 5.

The rear section of shaft 7 including the piston 2 is provided with two channels 18 and 19 which extend longitudinally through this section from a point near its rear end where each of them communicates with one of the connection fittings 6 on the distributor housing 5 through which the pressure medium may be supplied to or discharged from the cylinder chambers at the opposite sides of piston 2. For controlling the flow of pressure medium into and from these two chambers in cylinder 1 a valve unit including a pair of check valves 20 and 21 is mounted on shaft 7 and on piston 2 at the side of the latter which faces the cover of cylinder 1 and in a particular manner as will be subsequently described in detail.

For mounting this valve unit on shaft 7 and piston 2, the shaft is provided between the front surface of piston 2 and the section of shaft 7 which projects through the cover of cylinder 1 with a hub 39 through which a transverse bore 40 is drilled so that the axis of this bore 40 and the axis of shaft 7 intersect at right angles. Bore 40 is adapted to receive and to be filled out by the valve unit including the check valves 20 and 21, and therefore the diameter of hub 39 and the length of bore 40 are equal to the total length of the valve unit. Channels 18 and 19 in shaft 7 terminate at their front ends into the transverse bore 40 which also communicates with the two chambers of cylinder 1 at the opposite sides of piston 2 through axial bores 24 and 25 which extend in opposite directions into the two cylinder chambers through the wall of bore 40 and thus through a part of hub 39 and through piston 2, respectively.

Each of the two check valves 20 and 21 of the valve unit which is mounted in the bore 40 in hub 39 comprises a valve cage 26 or 27 which encloses a valve chamber 22 or 23, respectively. The bottom of each of these cages is provided with a bore forming an inner valve seat 28 or 29 which is normally closed by a valve disk or valve cone 32 or 33 under the action of a spring 30 or 31 and is adapted to be opened toward the inside of the respective valve chamber if a pressure medium, for example, compressed air or oil, is supplied through channel 18 or 19 under a sufficient pressure to overcome the strength of spring 30 or 31 so that it may then flow into one or the other cylinder chamber through a bore in the wall of the respective valve cage 26 or 27 and through a channel 24 or 25 which is in alignment with this bore. By being inserted into the same bore 40, the two check valves are disposed in axial alignment with each other and their valve cages 26 and 27 are separated from each other by a cylinder chamber 34 within a small tube 41 which when inserted into the bore 40 is disposed between the fr nt ends of channels 18 and 19 and in which a small control piston is slidable in the direction toward one or the other check valve 20 or 21. Each end of this small piston is provided with a projecting tappet pin 36 which is adapted to hit against the adjacent valve disk 32 or 33 and to lift the same off its seat 28 or 29 against the action of spring 30 or 31 when a pressure medium or a sufficient pressure is supplied through the respective channel 18 or 19 so as to act upon the end of the control piston 35 opposite to the end which carries the respective tappet pin which thereupon hits against the valve disk 32 or 33.

The three main components of the valve unit, i.e. the control tube 41 containing the control piston 35 and its tappets 36 and the two valve cages 26 and 27 containing the valve disks 32 and 33 and their seats 28 and 29 and springs 30 and 31,

may either be inserted consecutively into the bore 40 in hub 39 or they may be inserted in the form of a single element in which the valve cages 26 and 27 are secured to the intermediate tube 41. In either event, the entire valve unit has a total length which corresponds to the length of bore 40 and the diameter of hub 39. For securing this valve unit in a fixed position in the hub 39 of shaft 7, before the latter is inserted into cylinder 1, it is only necessary to slip a ring 42, preferably a spring ring, over the peripheral surface of hub 39 from the free end thereof. This ring 42 will then cover the opposite ends of the bore 40 and engage upon the outer ends of the valve cages 26 and 27.

Whereas in the copending application previously referred to the piston has a considerable thickness and is provided with a bore which extends diametrically through the entire piston and into the central part of which the valve unit has to be inserted, and into the wall of which annular grooves have to be cut into which small spring rings are to engage to lock the valve unit in a fixed position, it is evident from the foregoing description that by providing the shaft adjacent to the front side of the piston 2 with the hub 39 which only has a diameter equal to the length of the valve unit and contains a transverse bore 40 of the same length, the volume and weight of the piston and thus also the force required for sliding it back and forth relative to the cylinder 1, as well as the friction occurring during these movements are considerably reduced. Furthermore, the difficult operations previously required of cutting the annular grooves into the wall of the bore of the piston, of inserting the valve unit or its different elements deeply into this bore, and of then also inserting the small spring rings deeply into this bore and into the annular grooves are now avoided entirely since the valve unit or its three separate elements only need to be inserted into the short bore of the hub which has the same length as the valve unit, and the locking ring 42 may then be simply slipped over the hub to lock the valve unit in the exact position as required.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. In a rotary chucking cylinder for operating a chucking tool of a lathe or other machine tool comprising an outwardly closed cylinder having front and rear walls, each of said walls having a central bore, a piston axially slidable in and rotatable with said cylinder and dividing the inside thereof into two chambers, a shaft coaxially with said piston and having a front section and a rear section secured to the opposite sides of said piston and axially slidable in said central bores of said walls, sealing means between said walls and said shaft sections for sealing said chambers, said rear shaft section having a pair of channels extending from a point near the rear end of said shaft longitudinally through said entire rear shaft section and through at least a part of said piston, said rear shaft section having a part projecting to the 0b.. e of said cylinder, nonrotatable supply and discharge means connectcl o said outwardly projecting part of said rear shaft section and movable in the axial direction with said shaft for alternately supplying a fluid pressure medium to one of said channels and for ttemately discharging the return flow of said medium from the other channel, a valve unit mounted adjacent said piston and extending diametrically to said shaft and comprising a pair of check valves each having a valve chamber, the wall of each of said valve chambers having a first bore forming a valve seat and a second bore, said first bore of a fil. st of said valve chambers being adjacent to and communicating with the front end of a first of said channels, and the second bore of said first valve chamber communicating with one of said cylinder chambers, said first bore of the second valve chamber being adjacent to and communicating with the front end of the second channel, and the second bore of said second valve chamber communicating with the other cylinder chamber, a

valve member in each of said valve chambers and movable radially to the axis of said shaft, and a spring acting upon each of said valve members and tending to press said valve member upon its valve seat so as to close said first bore leading to the front end of the associated channel, a central control chamber intermediate said two valve chambers and valve seats, a small control piston slidable back and forth within said control chamber toward said two valve chambers and having a tappet pin projecting from each end adapted to hit against and lift that valve member off its seat toward which said control piston is moving, said front ends of said two channels terminating into said control chamber adjacent to the opposite ends thereof and at the opposite sides of said control piston, whereby when said pressure medium is supplied through a first of said channels into said control chamber, it lifts said first valve member off its seat and then passes through said first valve chamber to one of said cylinder chambers, while at the same time said pressure medium acts upon said control piston so that its tappet pin hits against and lifts said second valve member off its seat and thereby permits the pressure medium contained in said other cylinder chamber to flow out of the latter and back through said second valve chamber and said other channel; said chucking cylinder having the improvement comprising a hub on and coaxial to said shaft directly adjacent to said piston, said hub having a diameter larger than said two shaft sections and smaller than said piston, said hub having a transverse bore extending diametrically through said hub so that its axis and the axis of said shaft intersect substantially at right angles, said valve unit being inserted into said transverse bore before said shaft and piston is inserted into said cylinder and having a total length substantially equal to the length of said bore and the diameter of said hub, and a locking ring slipped over the peripheral surface of said hub from the free outer end thereof and covering the outer ends of said trans verse bore and substantially engaging with the opposite outer ends of said valve unit.

2. A chucking cylinder as defined in claim 1, in which said locking ring forms a spring ring exerting a compressive force upon said peripheral surface of said hub. 

1. In a rotary chucking cylinder for operating a chucking tool of a lathe or other machine tool comprising an outwardly closed cylinder having front and rear walls, each of said walls having a central bore, a piston axially slidable in and rotatable with said cylinder and dividing the inside thereof into two chambers, a shaft coaxially with said piston and having a front section and a rear section secured to the opposite sides of said piston and axially slidable in said central bores of said walls, sealing means between said walls and said shaft sections for sealing said chambers, said rear shaft section having a pair of channels extending from a point near the rear end of said shaft longitudinally through said entire rear shaft section and through at least a part of said piston, said rear shaft section having a part projecting to the outside of said cylinder, nonrotatable supply and discharge means connected to said outwardly projecting part of said rear shaft section and movable in the axial direction with said shaft for alternately supplying a fluid pressure medium to one of said channels and for alternately discharging the return flow of said medium from the other channel, a valve unit mounted adjacent said piston and extending diametrically to said shaft and comprising a pair of check valves each having a valve chamber, the wall of each of said valve chambers having a first bore forming a valve seat and a second bore, said first bore of a first of said valve chambers being adjacent to and communicating with the front end of a first of said channels, and the second bore of said first valve chamber communicating with one of said cylinder chambers, said first bore of the second valve chamber being adjacent to and communicating with the front end of the second channel, and the second bore of said second valve chamber communicating with the other cylinder chamber, a valve member in each of said valve chambers and movable radially to the axis of said shaft, and a spring acting upon each of said valve members and tending to press said valve member upon its valve seat so as to close said first bore leading to the front end of the associated channel, a central control chamber intermediate said two valve chambers and valve seats, a small control piston slidable back and forth within said control chamber toward said two valve chambers and having a tappet pin projecting from each end adapted to hit against and lift that valve member off its seat toward which said control piston is moving, said front ends of said two channels terminating into said control chamber adjacent to the opposite ends thereof and at the opposite sides of said control piston, whereby when said pressure medium is supplied through a first of said channels into said control chamber, it lifts said first valve member off its seat and then passes through said first valve chamber to one of said cylinder chambers, while at the same time said pressure medium acts upon said control piston so that its tappet pin hits against and lifts said second valve member off its seat and thereby permits the pressure medium contained in said other cylinder chamber to flow out of the latter and back through said second valve chamber and said other channel; said chucking cylinder having the improvement comprising a hub on and coaxial to said shaft directly adjacent to said piston, said hub having a diameter larger than said two shaft sections and smaller than said piston, said hub having a transverse bore extending diametrically through said hub so that its axis and the axis of said shaft intersect substantially at right angles, saiD valve unit being inserted into said transverse bore before said shaft and piston is inserted into said cylinder and having a total length substantially equal to the length of said bore and the diameter of said hub, and a locking ring slipped over the peripheral surface of said hub from the free outer end thereof and covering the outer ends of said transverse bore and substantially engaging with the opposite outer ends of said valve unit.
 2. A chucking cylinder as defined in claim 1, in which said locking ring forms a spring ring exerting a compressive force upon said peripheral surface of said hub. 